spring boot rabbitmq dead letter queue config not work - spring

Question

I config spring boot rabbit' dead letter queue, but ErrorHandler never receive any message. I search all the questiones about dead letter queue, but could not figure out. Can anyone help me ?
RabbitConfig.java to config dead letter queue/exchange:
#Configuration
public class RabbitConfig {
public final static String MAIL_QUEUE = "mail_queue";
public final static String DEAD_LETTER_EXCHANGE = "dead_letter_exchange";
public final static String DEAD_LETTER_QUEUE = "dead_letter_queue";
public static Map<String, Object> args = new HashMap<String, Object>();
static {
args.put("x-dead-letter-exchange", DEAD_LETTER_EXCHANGE);
//args.put("x-dead-letter-routing-key", DEAD_LETTER_QUEUE);
args.put("x-message-ttl", 5000);
}
#Bean
public Queue mailQueue() {
return new Queue(MAIL_QUEUE, true, false, false, args);
}
#Bean
public Queue deadLetterQueue() {
return new Queue(DEAD_LETTER_QUEUE, true);
}
#Bean
public FanoutExchange deadLetterExchange() {
return new FanoutExchange(DEAD_LETTER_EXCHANGE);
}
#Bean
public Binding deadLetterBinding() {
return BindingBuilder.bind(deadLetterQueue()).to(deadLetterExchange());
}
}
ErrorHandler.java to process DEAD LETTER QUEUE:
#Component
#RabbitListener( queues = RabbitConfig.DEAD_LETTER_QUEUE)
public class ErrorHandler {
#RabbitHandler
public void handleError(Object message) {
System.out.println("xxxxxxxxxxxxxxxxxx"+message);
}
}
MailServiceImpl.java to process MAIL_QUEUE:
#Service
#RabbitListener(queues = RabbitConfig.MAIL_QUEUE)
#ConditionalOnProperty("spring.mail.host")
public class MailServiceImpl implements MailService {
#Autowired
private JavaMailSender mailSender;
#RabbitHandler
#Override
public void sendMail(TMessageMail form) {
//......
try {
mailSender.save(form);
}catch(Exception e) {
logger.error("error in sending mail: {}", e.getMessage());
throw new AmqpRejectAndDontRequeueException(e.getMessage());
}
}
}

Answer 1

thx god, I finanlly find the answer!
all the configuration are correct, the problem is all the queues like mail_queue are created before I configure dead letter queue. So when I set x-dead-letter-exchange to the queue after the queue is created, it does not take effect.
中文就是，修改队列参数后，要删除队列重建！！！这么简单的一个tip，花了我几小时。。。。。。
How to delete queue, I follow the answer.
Deleting queues in RabbitMQ